1. Field of the Invention
The present invention relates to a connector for an optical fiber in which an optical fiber and an optical conversion element are detachably coupled together or optical fibers are detachably coupled each other, and particularly relates to the construction of a connector which can be simply assembled and inspected and repaired.
2. Description of the Prior Art
An optical information transmission system using optical fibers and optical conversion elements has been used increasingly. People expect much from optical fibers as one of information transmission lines which are less loss yet large capacity.
The optical information transmission system has to use a connector in order to couple the optical fiber to the optical conversion element or couple the optical fibers each other.
Among the connectors, the prior art means for coupling the optical conversion element to the optical will be described with reference to FIGS. 8 to 10.
A holding member 1 comprises a front tube portion 1a, a rear tube portion 1b and a flange portion 1c provided therebetween. a plurality of slits 1d are formed in an axial direction in the outer peripheral surface of the rear tube portion 1b, an optical fiber 2 is inserted through the rear tube portion 1 to hold the optical fiber 2 at the front tube portion 1a, and an optical fiber cable 3 coated by a coating portion 3a is held on the rear tube portion 1b. Then, a fixed tube 4 is fitted over the rear tube portion 1b to reduce the diameter of the rear tube portion 1b to lock the optical fiber cable 3. The front tube portion 1a of the holding member 1 is inserted into a tube portion 6a of an optical receptacle 6 internally provided with an optical conversion element 5, and a cap nut 7 having a projection 7a in the inner periphery thereof is threadedly engaged with the tube portion 6a of the optical receptacle 6 whereby the optical conversion element 5 and the optical fiber 2 may be detachably coupled.
However, the above-described prior art has the following difficulties.
In the past, the optical fiber cable 3 is inserted into the holding member 1 so that the fixed tube 4 is brought into fit in and contact with the rear tube portion 1b of the holding member 1, and therefore, the inner peripheral surface of the fixed tube 4 is merely secured in a surface contact state to the outer peripheral surface of the rear tube portion 1b. Thus, when an axial careless force is applied to the fixed tube 4 or after a lapse of the use, the fixed tube 4 is axially displaced and tends to be slipped out of the rear tube portion 1b.
Accordingly, when the fixed tube 4 is blindly moved, the optical fiber cable 3 being inserted into the rear tube portion 1b also tends to be slipped out. For this reason, the coupling efficiency of the optical fiber and optical conversion element or the mutual optical fibers ia deteriorated, thus bringing forth unfavorable results for the optical information transmission system.
There is previously proposed, as shown in FIG. 9, a system in which a shoulder 1e is provided on the outer peripheral surface of the rear tube portion 1b to prevent the fixed tube 4 from being slipped out. In this case, the optical fiber becomes hard to be slipped out of the holding member 1 but when the fixed tube 4 is once locked, it becomes difficult to remove the fixed tube 4 due to the presence of the shoulder 1e to make it impossible to separate the optical fiber from the holding member. Furthermore, since the work for mounting the fixed tube 4 is carried out, a rear portion of a cap nut has to be removed in advance, thus lacking in conditions of installing and removing operability required for the optical connector.